Piezoelectric fuse



June 21, 1966 J. RABlNow ETAL PIEZOELECTRIC FUSE Filed Oct. 17, 1951INVENTOR5-' Jacznb Rah-naw flinrheys 1 11.5 aund eraan the United Statesof America as represented by the Secretary of the Army Filed Oct. 17,1951, Ser. No. 251,807 3 Claims.` (Cl. 102-70.2)

The invention described herein may be manufactured and used by or forthe Government for governmental purposes without the payment of anyroyalty thereon.

This invention relates to a piezoelectric fuse for explosive missilesand more particularly to a piezoelectric fuse in combination with ashaped-charge missile.

In shaped-charge missiles itis necessary that the shapedcharge beinitiated at a predetermined distance, called the standoff distance,from the target in order to obtain optimum result. The stand-offdistance of such missiles employing point initiatingmeans is achieved bymeans of a windshield fastened to the body of the projectile andextending forwardly of the shaped-charge liner. Electrical connectionmust be made between the point initiating element xed in the tip of thewindshield and the detonator in the base of lthe shaped-charge. It hasbeen found that the connecting Wire forming the electrical connectionbetween point initiating element and the detonator which must beinsulated from the missile cannot be satisfactorily supported in themissile due to the load created by acceleration. It is impractical todevise supporting means for the connecting wire, especially 'since thesupporting means. must be cheap and simple to permit their use in massproduction.

The specific nature of the invention as well as other objects andadvantages thereof will clearly appear from the following description ofa preferred embodiment as shown in the accompanying drawings in which:

FIGURE l is a longitudinal cross-sectional view of an explosive missilein which the invention is incorporated.

- FIGURE 2 is an enlarged detail of the juncture and connection betweenthe cone shaped crystal supporting member and the missile body.

FIGURE 3 is an enlarged detail of the tip of the missile showing themounting means for the electrical generating means. FIGURE 4 is a planview of a -typical missile employi ing the invention.

Referring now to FIGURE l, a conductive windshield or ogive 1 of generalconical coniiguration is separated from a similarly conductive internalcone-shaped member 2 by an air space 3. These members are aflixed to amissile body 4 in a manner described in connection with FIGURE 3.

Between the apices of members 1 and 2 is a piezoelectric crystal 5supported by a rubber mounting 6 which is pierced to permit passage of aconnector 7. This assembly can be clearly seen in the detail drawing ofFIGURE 3. Rubber or rubber-like material i-s used as the mounting 6since it acts to absorb shocks of small magnitude,

but will transmit strong shocks such as would be caused by the missilestriking a target, and so would cause the generation of electricalenergy by transmitting such shock 'to the piezoelectric crystal 5 andcausing distortion thereof.

Referring now to FIGURE 2, the inner cone 2 of the nose assembly bearsagainst contact ring '14 to which is connected insulated conductingcable 9. Cable 9 passes through aligned holes in rings 12, 13 and 14 anda hole 11a in cone 11 and protective conduit 10 to a terminal 32 ofelectrical detonator 30 which is fixed in housing 8 intermediate 4theends thereof. As shown in FIGURE 1, hous- United States Patent() riceing 8 is located in the rear portion of explosive charge 118. Terminal32 is insulated from housing 8 and terminal 33 of the detonator issoldered to housing 8 as indicated by reference character 33a therebyproviding electrical connection between the detonator and body 4.Adjacent the detonator 30 is a first element 31a of an explosive train31.

The second element 31b of the explosive train is separated from element31a by means of housing 34 which contains a clockwork mechanism (notshown) and a third element 31C of the explosive train. normally held outof line with elements 31a and 31b by the clockwork mechanism. Theclockwork mechanism is activated by the forces of setback when `themissile is launched and after a predetermined period of time aligns thethird element with the rst and second elements. The explosive train 31,housing 34 and detonator 30 are -retained in housing 8 by means ofpotting compound 35. The inner cone 2 and contact ring 14 are insulatedfrom the body 4 by insulating ring 13 and insulating washer 15. Metallicsupport ring 12 provides abearing surface for the insulating ring 13.Threaded lock ring 16 clamps the assembly comprising the shaped-chargecone 1l1, inner cone 2 and rings 12, 13, 14 and 15 tightly against theshoulder 4a formed in the front end opening of the missile body 4.

Referring nowto FIGURE 3, 1the crystal mount 6 comprises a cup-shapedmember of rubber having a recess -19 formed therein in which is retaineda piezoelectric crystal 5. A resilient conductor 7 is formed with a head20` positioned in the recess in contact with the crystal. The legs 21-22of the conductor pass through an aperture 23 in the mount and are bentin opposite directions, conforming to outer surface of the mount. Themount -snugly tits the end 2a of the inner cone and holds the crystal inengagement with the inner cone. The legs 21-22 engage the inner surfaceof the apex of the windshield.

FIGURE 4 shows a typical configuration of a missile embodying theinvention wherein 1 is the windshield, 4 is the body and 17 is the tailassembly, it being understood that the invention is not limited to thisparticular c onfiguration.

In operation the missile is detonated when the nose por- -tion of themissile -strikes a target, setting up a shock wave in the crystal mountwhich is .transmitted therethrough to the crystal. Under the shock ofimpact the crystal is distorted and thereby generates electrical energywhich is transmitted to the electrical detonator 30 inhousing 8positioned in the explosive charge 18. The circuit is formed from oneside of the crystal by means of the inner cone 2 contact ring 14, andcable 9 which -is connected to terminal 32 of the electrical detonator,and from the other side of the crystal by means of conductor 7 incontact with the crystal and windshield, through the body of the missileand housing 8 to which the terminal 33 of the detonator is connected.

It will be apparent that the embodiment shown is only exemplary and thatvarious modifications can be made aflixed to said body but electricallyinsulated therefrom and in spaced relationship to the outer conicalmember, a resilient cup-shaped member having electrical energy meansixed therein mounted on the forward end of the inner conical member andin engagement with the inner The third element issurface of the apex ofthe outer conical member, the cupshaped member holding one terminal ofthe electrical generating means in contact with the inner conicalmember, the other terminal of the electrical generating means maintainedin contact with the outer conical member by means of a resilientconductor passing through an aperture in the cup-shaped member.

2. The invention of claim 1 wherein said electrical generating meanscomprises a ferro-electric crystal.

3. The combination of a detonator comprising a piezoelectric element, adetonating charge mounted in the base of a projectile, a windshieldaixed to the projectile, and circuit means connecting said element andsaid charge, said circuit means comprising said windshield having asimilar conic element positioned inside thereof in spaced relationshipthereto, said conic element being axed to said projectile by electricalinsulating means, an insulated cable extending -through the -body of theprojectile and l connecting said conic element and said charge, saidwindshield and body of the projectile forming the return circuit andsaid circuit means, said piezoelectric element resiliently mountedbetween the apices of the Windshield and the conic element in electricalcontact therewith.

References Cited by the Examiner UNITED STATES PATENTS 2,764,091 9/1956Hudson 102-702 FOREIGN PATENTS 277,052 8/ 1951 Switzerland.

BENJAMIN A. BORCHELT, Primary Examiner.

SAMUEL BOYD, Examiner.

D. D. DOTY, W. C. ROCH, Assistant Examiners.

3. THE COMBINATION OF A DETONATOR COMPRISING A PIEZOELECTRIC ELEMENT, ADETONATING CHARGE MOUNTED IN THE BASE OF A PROJECTILE, A WINDSHIELDAFFIXED TO THE PROJECTILE, AND CIRCUIT MEANS CONNECTING SAID ELEMENT ANDSAID CHARGE, SAID CIRCUIT MEANS COMPRISING SAID WINDSHIELD HAVING ASIMILAR CONIC ELEMENT POSITIONED INSIDE THEREOF IN SPACED RELATIONSHIPTHERETO, SAID CONIC ELEMENT BEING AFFIXED TO SAID PROJECTILE BYELECTRICAL INSULATING MEANS, AN INSULATED CABLE EXTENDING THROUGH THEBODY OF THE PROJECTILE AND CONNECTING SAID CONIC ELEMENT AND SAIDCHARGE, SAID WINDSHIELD AND BODY OF THE PROJECTILE FORMING THE RETURNCIRCUIT AND SAID CIRCUIT MEANS, SAID PIEZOELECTRIC ELEMENT RESILIENTLYMOUNTED BETWEEN THE APICES OF THE WINDSHIELD AND THE CONIC ELEMENT INELECTRICAL CONTACT THEREWITH.